Magnetic solid-phase extraction of neonicotinoid pesticides from pear and tomato samples using graphene grafted silica-coated Fe3O4 as the magnetic adsorbent

A novel graphene grafted silica-coated Fe3O4 (Fe3O4@SiO2-G) was synthesized and used as an efficient magnetic solid-phase extraction adsorbent for the simultaneous extraction of four neonicotinoid pesticides (thiamethoxam, imidacloprid, acetamiprid and thiacloprid) from pear and tomato samples followed by high performance liquid chromatography-diode array detection. After extraction, the adsorbent could be conveniently separated from the sample solution by an external magnetic field. The main experimental parameters affecting the extraction efficiency were investigated in detail. Under the optimum conditions, a rapid and effective determination of the neonicotinoid pesticides in pear and tomato samples was achieved. The limits of detection (S/N = 3) of the method for the neonicotinoids ranged from 0.08 to 0.15 ng g(-1). Good linearity and reproducibility were obtained. The recoveries of the method were in the range from 93.1% to 107.4%.